The invention relates to the influence of nucleobases on the immune function.
Purines and pyrimidines are synthesized in cells with amino acids as the principal precursors. It has now been found that a depressed immune response in mammals can be reversed by the addition of a nucleobase source to the formulation. In has also been found that the presence of nucleobases in the diet can prevent the immune suppression that occurs with protein or amino acid starvation. The prior art has maintained that the role of the nucleobases was to aid in utilization of protein or amino acids. As this invention demonstrates, this is clearly not true.
The stimulating effect of nucleobase sources on the immune system has been demonstrated by tests, e.g. in mice having depressed T lymphocyte function due to protein malnutrition. Further animal tests show that the depressed immune function of animals placed on a protein free diet cannot sufficiently be restored by protein repletion alone--even though this allows restoration of body weight--but requires the administration of a nucleobase source.
The invention provides a method of maintaining the immune function in the human and animal body even in the face of adverse nutrition including exclusion of amino acid or protein sources. Addition of the nucleobases allows maintenance of immune function under protein or amino acid starvation. The nucleobase source may be administered by any conventional route in solid or liquid form, in particular enterally, e.g. orally or nasally, or parenterally, e.g. in the form of injectable solutions or suspensions.
For use according to the invention the nucleobase source may be administered in conventional pharmaceutically or nutritionally acceptable formulation form. Examples of conventional pharmaceutically acceptable formulation forms include tablets, capsules and injectable forms which may contain the active agent in admixture with conventional pharmaceutically acceptable excipients, e.g. inert diluents or carriers, such as calcium carbonate, lactose and talc, granulating and disintegrating agents, e.g. starch and algenic acid, flavouring, colouring and sweetening agents, binding agents, e.g. starch or gelatin, lubricating agents, e.g. magnesium steratte and talc.
Examples of conventional nutritionally acceptable formulation forms include conventional diets, e.g. formula diets containing the nucleobase source in admixture with sources for essential amino acids and energy supply such as for proteins, carbohydrates and/or fat as desired.
Such dietary compositions may for example supply from 400 to 2000 Kcal, e.g. 1500 Kcal per day. The compositions of the inventions may be enriched with vitamins, such as vitamin C, minerals, such as iron, trace elements such as Selenium and optionally other elements, depending on the needs of the subject to be treated.
Formulations for enteral application are conveniently in solid or liquid form.
Nucleobase sources suitable for use in the method of the invention comprise, and more preferably consist essentially of natural nucleobases, nucleosides, nucleotides, RNA, DNA, equivalents thereof and/or mixtures comprising one or more of these compounds.
Natural nucleobases include but are not limited to the purines adenine and guanine as well as the pyrimidines cytosine, thymine and uracil.
Natural nucleosides include but are not limited to the ribose nucleosides adenosine, guanosine, uridine and cytidine and the deoxyriboase nucleosides deoxyadenosine, deoxyguanosine, deoxythymidine and deoxycytidine.
Natural nucleotides include but are not limited to phosphate esters of natural nucleosides, such as the monophosphates adenylate (AMP), guanylate (GMP), uridylate (UMP), cytidylate (CMP), deoxythymidylate (dTMP) deoxycytidylate (dCMP), and dipphosphates and triphosphates of natural nucleosides such as ADP and ATP.
The amount of nucleobase source to be administered will i.e. depend on the type of treatment desired, e.g. whether prophalactic or therapeutic, and on the subject to be treated, e.g. the eating habits of the individual, whether the subject to be treated is a child or adult and the like. Thus, a heavy meat eater will possibly have greater nucleobase source supply requirements than a person on a vegetable diet. In general, for larger mammals including humans, satisfactory results will be obtained with 1 to 50 times the normal daily amount of ca. 0.5 to 1.5 g RNA corresponding with about 0.1 to 75 g RNA, DNA, nucleosides or nucleotides per day or an equivalent amount in the form of nucleobases.
For the purpose of this invention one weight unit of nucleobase is regarded to be equivalent with 2.5 to 3 weight units of RNA, DNA, nucleosides or nucleotides. For convenience, the following daily amounts are expressed in g RNA only.
For long term or nutritional use, the daily amount of nucleobase source to be administered will conveniently vary within the range of from 0.1 to 4 g RNA, preferably of from 1 to 3 g RNA, in particular of from 1.5 to 2.5 g RNA.
For short term or therapeutical use, the daily amount will in general be higher. For acute treatment with high amounts of nucleobase sources, it is preferred to employ pyrimidine nucleobase sources such as uridine or uracil. Preferred daily amounts for therapeutic use are from 100% to 2000% in excess of normal amounts, corresponding with from about 0.5 g to 30 g RNA. More preferred amounts for therapeutical use are in the range of from 1 g to 20 g RNA, in particular of from 1 g to 7.5 g RNA per day. Pharmaceutical compositions may compromise a daily amount or parts thereof, e.g. in unit doses suitable for three or four applications per day.
The method and compositions of the invention may be employed in any situation where a stimulation of the immune function is desirable, e.g. for restoring a normal immune response, for abating the immunosuppressive effect of an immunosuppressant agent, for enhancing the development of the immune system in a developing mammal, for enchancing the activity of senescent immune system of a mammal and the like.
In the following examples, tables and figures illustrating the invention:
F is standard laboratory chow supplied by Purina under the code number 5008 and comprising 23.5% weight of a protein source from soybean, fish-bone meal and milk. PA0 NF is a nucleotide free diet supplied by Purina under the number 5755, comprising 21% by weight of casein as its protein source and only traces (less than 0.001% by weight according to HPLC analysis) of nucleotides. NF is is isocaloric and isonitrogenous with F. PA0 NFR is NF supplemented with RNA (purified yeast RNA). PA0 NFR (0.25%) is NFR supplemented with 0.25% by weight purified yeast RN. PA0 NFA is NF supplemented with adenine. PA0 NFU is NF supplemented with uracil. PA0 PF is NF without protein, supplied by Purina under the code number 5765. PA0 PFR is PF supplemented with RNA (purified yeast RNA) PA0 PFA is PF supplemented with adenine. PA0 PFU is PF supplemented with uracil. PA0 PLN stands for popliteal lymph nodes.